1. Field of the Invention
The present invention relates to a high brightness light emitting diode, in which gallium phosphide is provided as a window.
2. Related Prior Art
For manufacturing light emitting diodes, it's very important to promote brightness. Gallium phosphide (GaP) is a material with good electrical conductivity and high transparency in wavelength ranging from red to green, and therefore frequently applied to light emitting diodes (LEDs).
FIG. 8 shows a conventional LED structure including GaP. In this structure, a SiO2 layer 82, a reflective metal layer 83, a GaP layer 84, an active layer 85 and a gallium arsenide (GaAs) window 86 are sequentially presented on the silicon substrate 81. The electrodes 87, 88 are respectively formed on the GaAs window 86 and below the silicon substrate 81. The GaP material is provided here, but unfortunately doesn't contribute to brightness of the LED.
U.S. Pat. No. 5,869,849 provides another LED structure and method for producing the same, in which the GaAs substrate can be removed once a GaP layer is epitaxed on the active layer of aluminum gallium indium phosphide (AlGaInP). Next, the epitaxial structure is directly bonded to a GaP substrate, and two electrodes are respectively formed on the GaP epitaxial layer and below the GaP substrate. According to such a structure, the GaP window may theoretically enhance brightness of the LED. However, lattice alignment is difficult and bonding directly to the epitaxial layer at high temperature will seriously decrease production yield.
Therefore, it is necessary to find a method for producing LEDs with GaP windows, so that the above disadvantages can be meliorated.